The tropical disturbance (Invest 93L) that crossed over Florida on Wednesday, bringing welcome rains of 1 - 3 inches, is now a naked swirl of low clouds over the central Gulf of Mexico. The disturbance is embedded in a large area of dry air associated with an upper level low pressure system, and this dry air is discouraging development. 93L is also moving into a region of moderate wind shear of 10 - 20 knots, and NHC is giving 93L a 0% chance of developing into a tropical depression before the storm makes landfall in Mexico south of Brownsville on Saturday. There are a few heavy thunderstorms trying to fire up near the center of 93L's fairly well-formed circulation, but I don't think this storm is going to bring more than 1 - 2 inches of rain to the coast on Saturday.

Central Caribbean disturbance 94LDisorganized heavy thunderstorm activity continues in the region between Central America and Jamaica. Wind shear has fallen to the moderate range, 10 - 20 knots, and is predicted to continue to fall over the next two days. This should allow the disturbance, dubbed Invest 94L by NHC on Friday afternoon, to increase in organization, though it will take many days for it to approach tropical depression status, since it is so large and poorly organized. The last two runs of the NOGAPS model have developed the disturbance into a tropical depression or storm by early next week, with the system moving northwards into Jamaica, the Cayman Islands, and eastern Cuba. The other major models do not show the disturbance developing during the coming week. NHC is giving the disturbance a 10% of developing into a tropical depression by Sunday. A surge of moisture accompanying a tropical wave may aid development when the wave arrives in the Western Caribbean on Sunday. Water temperatures in the Central Caribbean are about 1°C above average, 29°C, which is plenty warm enough to support development of a tropical storm. Residents of Jamaica, eastern Cuba, the Cayman Islands, Haiti, and the Dominican Republic should anticipate the possibility that heavy rains of 2 - 4 inches may affect them today through Sunday.

Five EF-5 tornadoes confirmed in 2011The National Weather Service in Oklahoma City announced Wednesday that the violent tornado that hit Binger, El Reno, Peidmont, and Guthrie, Oklahoma on May 24, killing nine people, was an EF-5 with winds greater than 210 mph. The rating was given based on measurements made by a University of Oklahoma portable "Doppler on wheels" radar. The long track, large wedge tornado caused extensive damage, with well built houses cleanly swept from their foundation and trees debarked. This tornado brings the total number of EF-5 tornadoes this year to five, tying 2011 with 1953 for 2nd place for greatest number of these top-end tornadoes in one year. Only 1974 (six) had more. The EF-5 tornadoes of 2011:

- The April 25 - 28 tornado outbreak, with 330 tornadoes, was the largest tornado outbreak of three days or less duration on record. The previous record was 148 tornadoes, set during the April 3 - 4, 1974 Super Outbreak.

- For April 27, 186 tornadoes have been confirmed. This is the largest 1-day tornado total on record, beating the 148 recorded in 24 hours on April 3 - 4, 1974.

- The April 14 - 16 tornado outbreak, with 162 confirmed tornadoes, ranks as the fourth largest tornado outbreak of three days or less duration on record.

- April confirmed tornado total was 683, making it the busiest tornado month on record. The previous record was 542 tornadoes, set in May 2003. The previous April record was 267 tornadoes, which occurred in April 1974. The 30-year average for April tornadoes is 135.

- If the three deaths in Massachusetts from Wednesday's tornadoes are confirmed, this year's tornado death toll will be 522, beating 1953 as the deadliest tornado year since modern tornado records began. That year, 519 people died, and three heavily populated cities received direct hits by violent tornadoes. Waco, Texas (114 killed), Flint, Michigan (115 killed), and Worcester, Massachusetts (90 killed) all were hit by violent F-4 or F-5 tornadoes. A similar bad tornado year occurred in 1936, when violent tornadoes hit Tupelo Mississippi (216 killed), and Gainesville, Georgia (203 killed.) During that time period, the tornado death rate per million people was 60 - 70 times as great as in the year 2000 (Figure 4), implying that this year's tornadoes would have killed many thousands of people had we not had our modern tornado modern warning system.

- The May 22, 2011 Joplin, Missouri tornado killed 138 people and injured 1150, making it the deadliest U.S. tornado since 1947, and 8th deadliest in history. The $1 - $3 billion estimate of insured damage makes it the most expensive tornado in history.

- Damage from the April 25 - 28 super tornado outbreak was estimated at $3.5 - $6 billion, making it the most expensive tornado outbreak of all-time.

- The tornado that hit Springfield, Massachusetts on June 1 was at least an EF-3 with 136 - 165 mph winds. It was only the 9th EF-3 or stronger tornado to hit Massachusetts since 1950, and the third deadliest, with three deaths.

- The year 2011 now ranks in 3rd place behind 1974 and 1965 for highest number of strong to violent EF-3, EF-4, and EF-5 tornadoes (Figure 3.)

Figure 3. Number of strong to violent EF-3, EF-4 and EF-5 tornadoes from 1950 to 2011. The year 2011 now ranks in 3rd place behind 1974 and 1965. There is not a decades-long increasing trend in the numbers of these most dangerous of tornadoes. Image credit: NOAA/National Climatic Data Center (updated using stats for 2008 - 2011 from Wikipedia.)

Figure 4. Death rate per million people per year in U.S., 1875-2000. Thin line with dots is raw rate, curved thick line is death rate, filtered by 3-point median and 5-point running mean filter, and straight solid lines are least squares fit to filtered death rate for 1875-1925 and 1925-2000. Dashed lines are estimates of 10th and 90th percentile death rates from 1925-2000. The death rate fell from 8 per million to .12 per million between 1940 and 2000. Image credit: A Brief History of Deaths from Tornadoes in the United States, Harold Brooks and Charles Doswell III.

Joplin tornado the 7th U.S. billion-dollar weather disaster of 2011The Joplin tornado is the 7th U.S. weather disaster of 2011 costing more than a billion dollars. With a major flooding disaster coming on the Missouri River, and hurricane season still to come, 2011 has an excellent chance of beating 2008's record of nine billion-dollar weather disasters. The billion dollar weather disasters of 2011 so far:

The next U.S. billion-dollar weather disaster: a Missouri River flood?A great 100-year flood has arrived along the Missouri River and its tributaries from Montana to Nebraska. Record spring rains, combined with snow melt from record or near-record winter and spring snows, brought the Missouri River at Williston, North Dakota to 27.9' yesterday, just an inch short of the highest crest on record (28.0' on 4/01/1912.) Tributaries to the Missouri, such as the Souris River in North Dakota and the North Platte River in Nebraska, are already flooding at all-time record heights. With warm summer temperatures and additional rainfall expected over much of the area during the coming week, snow melt and rain runoff will swell area rivers even further, creating a damaging 100-year flood. Wunderground weather historian Christopher C. Burt has the details in his latest post, and I will be writing more on this latest epic flood next week.

I'll have a new post on Monday, or earlier if the Caribbean disturbance shows significant development.

Until someone reports pressures beginning a falling trend below 1007mb, I probably won't get too excited. This system has been very status quo for many days now. That pressure has been rock steady.

All agreed. These monsoonal lows will drive you crazy waiting for development to happen. The two things it has going for it is a fairly vigorous ( but broad ) circulation that is producing fresh NE winds even where I am and lots of warm water to feed the system once it gets cranking.

Quoting kmanislander:This buoy is about 180 miles immediately East of the "center" of the low. While the winds there are nothing to crow about it does show a gradual increase over time.

Its still recovering from the time when convection waned yesterday, as shown with the corresponding decrease of wind speed, as continues to increase gradually so should convection, but it wont continue increasing if convection wanes at dimn.

Quoting HimacaneBrees:Help me out folks. In March i reserved a condo at Gulf Shores. We check in on the 9th (this Thursday). I did not purchase trip insurance. Which was my stupid idea I didn't think we'd need it. What are the chances of 94L becoming something and ruining my families vacation?

You will have "Lots Of Fun There" Waters are warm and Beautiful.... You might have the Normal afternoon Thunder storms but that will be it... Enjoy your self with the Family, and Catch some "Fish"....

There is always a possibility when you have a well-defined circulation sitting in the Caribbean for a week. We still have at least 5 days before being rid of the thing, so it should be watched, but chances of development look low right now.

Thankyou...

We will wait and see what Jeff has to say about this on Sunday or Monday.

You know what they say. You can't bake a cake without all of the ingredients. Now that shear has eased off the dry air is the impediment. If the thunderstorms had a chance to build the surface pressure would fall thus increasing the winds and getting the cycle going.

With the heat of the day in full swing 94L will probably just hold its own until after nightfall.

Until someone reports pressures beginning a falling trend below 1007mb, I probably won't get too excited. This system has been very status quo for many days now. That pressure has been rock steady.

Grothar, Shen, etymology is like epistemology. You start down that road and the only plausible outcome is heavy anti-psychotics and insane asylums. Spelunk that rabbit hole with care and plenty of proverbial bread crumbs.

Quoting Levi32:ASCAT shows a giant area of very light winds over much of the Caribbean. Such a large region of light winds implies very little surface convergence, or piling up of air, except for the directional convergence along the monsoon trough, which is where all of the convection currently lies. Without a focused area of convergence, it will be hard for 94L to gain significant convection around it, despite an otherwise semi-favorable atmospheric pattern.

Quoting Bitmap7:

Really, because there is nil convergence going on and we all know how important that is in building thunderstorms.

I agree with Jedkins that moisture over the West side of the system isn't as big of an issue as people have been saying it is. The Water Vapor image from GOES satellites is useful for many, many things, but for determining atmospheric moisture it is terrible. The image only shows the very upper level of the atmosphere and gives you no idea of the moisture in the mid to lower levels of the atmosphere. Nonetheless, moisture over 93l is still an issue.

Bitmap posted this upper air image over Cayman island earlier

This image clearly shows that the atmosphere above about 600 mb has been relatively dry for the last 36 hours. This idea is also reflected on the TPW which Jedkins mentioned as showing a moist environment

Look off the coast of the Yucatan peninsula and you can see that it is fairly dry and also that that air is being pulled in by the low which is noted by the end of the loop where drier air is visible off of the coast of Nicaragua and Honduras.

Another thing is midlevel sheer over the Western half

The upper air sounding over Cayman island posted above also shows midlevel sheer.

So, midlevel moisture and sheer both seem to be the main problems suppressing convection on the west side of this low.

However, if you look again at the upper air sounding over the Cayman island and the TPW loop, moisture does appears to be improving over the region. Mid level sheer also appears to be going down, here was the mid level sheer map 24hrs ago

Indeed this is true, however, is there a possibility that this broad area of circulation could tighten up? Take a guess, you might suprise yourself... XD

There is always a possibility when you have a well-defined circulation sitting in the Caribbean for a week. We still have at least 5 days before being rid of the thing, so it should be watched, but chances of development look low right now.

Quoting Levi32:ASCAT shows a giant area of very light winds over much of the Caribbean. Such a large region of light winds implies very little surface convergence, or piling up of air, except for the directional convergence along the monsoon trough, which is where all of the convection currently lies. Without a focused area of convergence, it will be hard for 94L to gain significant convection around it, despite an otherwise semi-favorable atmospheric pattern.

Quoting Levi32:ASCAT shows a giant area of very light winds over much of the Caribbean. Such a large region of light winds implies very little surface convergence, or piling up of air, except for the directional convergence along the monsoon trough, which is where all of the convection currently lies. Without a focused area of convergence, it will be hard for 94L to gain significant convection around it, despite an otherwise semi-favorable atmospheric pattern.

Indeed this is true, however, is there a possibility that this broad area of circulation could tighten up? Take a guess, you might suprise yourself... XD

Invest 94L looks less impressive than it did this time yesterday in my opinion. I'm becoming less optimistic in regards to development into a tropical depression than I was yesterday. Pretty fragile system with no real direction and no real strong dynamics supporting it outside of the monsoon trough, slightly lower upper level winds, and warm waters.

94L is going to take a long time to develop if it even gets to that stage...The shear is still prevelant in the area and is prohibiting development..If it does develop i think we are looking at thursday or friday and i see a ne movement due to that strong trough scheduled to be in the area at the time..The tropics are quiet at the present time...

Quoting HimacaneBrees:Help me out folks. In March i reserved a condo at Gulf Shores. We check in on the 9th (this Thursday). I did not purchase trip insurance. Which was my stupid idea I didn't think we'd need it. What are the chances of 94L becoming something and ruining my families vacation?

go have your vacation this is not something to worry in the short term

Quoting Levi32:ASCAT shows a giant area of very light winds over much of the Caribbean. Such a large region of light winds implies very little surface convergence, or piling up of air, except for the directional convergence along the monsoon trough, which is where all of the convection currently lies. Without a focused area of convergence, it will be hard for 94L to gain significant convection around it, despite an otherwise semi-favorable atmospheric pattern.

Hi Levi

You know what they say. You can't bake a cake without all of the ingredients. Now that shear has eased off the dry air is the impediment. If the thunderstorms had a chance to build the surface pressure would fall thus increasing the winds and getting the cycle going.

With the heat of the day in full swing 94L will probably just hold its own until after nightfall.

Help me out folks. In March i reserved a condo at Gulf Shores. We check in on the 9th (this Thursday). I did not purchase trip insurance. Which was my stupid idea I didn't think we'd need it. What are the chances of 94L becoming something and ruining my families vacation?

Quoting Levi32:ASCAT shows a giant area of very light winds over much of the Caribbean. Such a large region of light winds implies very little surface convergence, or piling up of air, except for the directional convergence along the monsoon trough, which is where all of the convection currently lies. Without a focused area of convergence, it will be hard for 94L to gain significant convection around it, despite an otherwise semi-favorable atmospheric pattern.

Quoting beell:PW values in the entire column for 94L are definitely tropical. But you can stil have a dry layer 1-2km thick that will squash convection and not change the total PW value that much. Many times, it is difficult to see or evaluate moisture from a water vapor loop. The brightest, highest clouds are all that is visible. You really can't see much underneath.

Take a look at the floater wv loop along 15N on the west side of 94L. Note the greyish looking water vapor early in the loop. This is lower in the atmosphere than the brighter whites. Note how it begins to turns dark and fade away. The water vapor sensed by the satellite is evaporating.

Dry air is present on the west side imo. No different than what the NHC has been saying.

Well, it looks like NHC quotes dry air as the inhibitor in their latest outlook.. I still think your explanation was good though Jedkins.

Well yes the NHC said there was dry air in the mid levels, but so did I.

The NHC isn't going to put into their discussion a complex detailed reason explaining the lack of convection, but essentially the dry layer is only there due the storm's lack of organization, not dry air itself. Because the overall atmospheric moisture through the column is very high there.

Quoting Seflhurricane:putting things into prospective, if 94L indeed follows the computer models towards cuba and the northwest carribean florida is going to get desperatly needed rain. as for its organization it is quite ragged right now and i have not seen any improvement since mid morning, the center of circulation needs become better defined

And it is better defined, plus convection is wrapping around from the SW end.

It will also look better tomorrow, much better when a tropical wave moving in from the east will aide 94L greatly in development.

putting things into prospective, if 94L indeed follows the computer models towards cuba and the northwest carribean florida is going to get desperatly needed rain. as for its organization it is quite ragged right now and i have not seen any improvement since mid morning, the center of circulation needs become better defined

I am in Northern Broward. FLL. It really is the driest I have ever seen it. This is the God's honest truth. When I water some plants, the geckos actually come down and start drinking the water on the leaves. Never saw that in my life. Hope we get a soaker. P.S. The coastal areas are much drier. We haven't had a drop.

Good for beachgoers, they won't have to run for shelter, plus there are thousands on the beach at this time of year, and getting them to safety when it storms would be chaotic. That is, if there is anything good coming out of this drought.